Add day 22 solution

Author: SkiFire13

src/day22.rs

@@ -0,0 +1,127 @@
+#[allow(unused_imports)]
+use super::prelude::*;
+type Input = Vec<((usize, usize, usize), (usize, usize, usize))>;
+
+pub fn input_generator(input: &str) -> Input {
+    input
+        .lines()
+        .map(|line| {
+            let (x1, y1, z1, x2, y2, z2) = line
+                .split(&[',', '~'][..])
+                .map(|n| n.parse().unwrap())
+                .collect_tuple()
+                .unwrap();
+            ((x1, y1, z1), (x2, y2, z2))
+        })
+        .collect()
+}
+
+pub fn part1(input: &Input) -> usize {
+    let mut input = input.clone();
+    input.sort_by_key(|&((x, y, z), _)| (z, x, y));
+
+    let mut maxx = 0;
+    let mut maxy = 0;
+
+    for &((x1, y1, _), (x2, y2, _)) in &input {
+        maxx = max(maxx, x1);
+        maxy = max(maxy, y1);
+        maxx = max(maxx, x2);
+        maxy = max(maxy, y2);
+    }
+
+    let mut supported_by = FxHashSet::default();
+
+    let mut supporting = vec![false; input.len()];
+    let mut last = vec![(usize::MAX, 0); (maxx + 1) * (maxy + 1)];
+
+    for (i, &((x1, y1, z1), (x2, y2, z2))) in input.iter().enumerate() {
+        let mut z_target = 0;
+        for x in x1..x2 + 1 {
+            for y in y1..y2 + 1 {
+                z_target = max(z_target, last[y * (maxx + 1) + x].1)
+            }
+        }
+
+        for x in x1..x2 + 1 {
+            for y in y1..y2 + 1 {
+                let (s, l) = last[y * (maxx + 1) + x];
+                if l == z_target && s != usize::MAX {
+                    supported_by.insert(s);
+                }
+                last[y * (maxx + 1) + x] = (i, z_target + z2 - z1 + 1);
+            }
+        }
+        if supported_by.len() == 1 {
+            supporting[*supported_by.iter().next().unwrap()] = true;
+        }
+        supported_by.clear();
+    }
+
+    supporting.iter().filter(|&&sup| !sup).count()
+}
+
+pub fn part2(input: &Input) -> usize {
+    let mut input = input.clone();
+    input.sort_by_key(|&((x, y, z), _)| (z, x, y));
+
+    let mut maxx = 0;
+    let mut maxy = 0;
+
+    for &((x1, y1, _), (x2, y2, _)) in &input {
+        maxx = max(maxx, x1);
+        maxy = max(maxy, y1);
+        maxx = max(maxx, x2);
+        maxy = max(maxy, y2);
+    }
+
+    let mut under = vec![FxHashSet::default(); input.len()];
+    let mut over = vec![FxHashSet::default(); input.len()];
+    let mut last = vec![(usize::MAX, 0); (maxx + 1) * (maxy + 1)];
+
+    for (i, &((x1, y1, z1), (x2, y2, z2))) in input.iter().enumerate() {
+        let mut z_target = 0;
+        for x in x1..x2 + 1 {
+            for y in y1..y2 + 1 {
+                z_target = max(z_target, last[y * (maxx + 1) + x].1)
+            }
+        }
+
+        for x in x1..x2 + 1 {
+            for y in y1..y2 + 1 {
+                let (s, l) = last[y * (maxx + 1) + x];
+                if l == z_target && s != usize::MAX {
+                    over[s].insert(i);
+                    under[i].insert(s);
+                }
+                last[y * (maxx + 1) + x] = (i, z_target + z2 - z1 + 1);
+            }
+        }
+    }
+
+    let mut sum = 0;
+    let mut queue = VecDeque::new();
+    let mut seen = FxHashSet::default();
+    for i in 0..input.len() {
+        queue.extend(over[i].iter().copied());
+        seen.clear();
+        seen.insert(i);
+
+        'outer: while let Some(brick) = queue.pop_front() {
+            if seen.contains(&brick) {
+                continue;
+            }
+
+            for u in &under[brick] {
+                if !seen.contains(u) {
+                    continue 'outer;
+                }
+            }
+
+            sum += 1;
+            seen.insert(brick);
+            queue.extend(over[brick].iter().copied());
+        }
+    }
+    sum
+}

src/main.rs

@@ -20,7 +20,7 @@ aoc_helper::main!(2023 =>
     day19,
     day20,
     day21,
-    // day22,
+    day22,
     // day23,
     // day24,
     // day25,